One of the main tenets of evolutionary biology is that organisms behave so as to maximize the number of their genes that will be passed on to future generations. Parents often produce more offspring than they can rear in case special opportunities or calamities occur. This frequently leads to deprivations and even death of some offspring. This book is about the evolutionary diversity, importance, and consequences of such squeezes. The authors, experts in their field, review the theory, field experiments, and natural history of sibling rivalry across a broad sweep of organisms, in a clear and accessible style that should appeal to both academics and natural historians.